Another 124,511 people presented themselves at ports of entry, many seeking humanitarian protection, but immigration officials found them inadmissible.

In 2000, however, more than 1.6 million illegal border crossers were apprehended. In 2001, the figure was 1.3 million.

In the early 2000s, the largest group of undocumented migrants caught entering the US were Mexican men crossing to work. When caught, border patrol sent them back without long-term detention or court proceedings.

Many crossed again and again and some eventually succeeded in evading border enforcement. The high apprehension numbers certainly include many individuals caught and counted more than once.

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Small ups and downs in the flow continued until a significant drop off at the end of the decade – from 556,041 in 2009 to 340,252 in 2011 – coinciding with the great recession, and the disappearance of the jobs many migrants came for.

In the following years, apprehension numbers continued to fluctuate between 350,000-500,000, with a low of 310,531 in 2017.

Observers attribute that steep decline to economic growth in Mexico, ramped-up border enforcement, and the “Trump effect”, which deterred some migrants.

Young people fled gang recruitment, persecution by police working with organized crime, and threats of rape and death. Mothers and fathers undertook the arduous journey to escape the dangers posed by corrupt officials, gangs and security forces.

Unlike adults crossing the border looking for work, families with children and individuals seeking asylum cannot be deported quickly; asylum takes months and years in immigration court.

Adults are often detained for the duration of the legal process, but current law forbids the government from detaining children for long periods.

The government can detain families together, but it doesn’t have nearly enough space to hold all of the families now coming. CBP apprehension statistics released on Tuesday for fiscal year 2018 show steep increases in recent months – mostly families with children – a total of 16,658 people in September alone.

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Here on the border, Trump’s hardline rhetoric collides with the reality of thousands of refugee families already here who cannot be imprisoned indefinitely, nor can they be quickly removed, at least according to current law.

Churches and other volunteers gladly shelter those set free because the government’s immigration prisons are full.